NASA Joy As Probe Orbits Dwarf Planet Ceres

The NASA probe Dawn has begun orbiting the dwarf planet Ceres in a major triumph for the US space agency.

It is the first time in the history of space exploration that a probe has made it to a dwarf planet.

"It went exactly the way we expected. Dawn gently, elegantly slid into Ceres' gravitational embrace," said mission chief engineer Marc Rayman at NASA's Jet Propulsion Laboratory.

Ceres, which lies in the asteroid belt between Mars and Jupiter, is Dawn's final destination.

It will spend the next 16 months photographing the icy surface after previously exploring the asteroid Vesta.

The probe sent back stunning close-ups of its lumpy surface before moving on to Ceres, which is roughly the size of Texas.

As Dawn approached Ceres, it beamed back puzzling images revealing two bright spots inside a crater - signs of possible ice or salt.

Scientists hope to get a better glimpse when it gets closer to the surface to study whether plumes of water vapour seen earlier are still venting.

Dawn is currently in Ceres' shadows and will not start taking new pictures until it emerges in April, Mr Rayman said.

He added: "The real drama is exploring this alien, exotic world."

Since its launch in 2008, Dawn has travelled three billion miles, made possible by its ion propulsion engines.

They provide gentle, yet constant acceleration and are more efficient than conventional thrusters.

Dwarf planets have recently become the focus of space exploration.

This summer, another NASA spacecraft, New Horizons, is set to make the first visit to Pluto, which has been demoted to dwarf planet.

Dawn almost never got off the ground after funding problems and launch delays.

The seven-year mission has cost $473m (£313m).